Method of copy detection and protection using time jumps

ABSTRACT

The invention relates to a method of copy detection of a record carrier wherein time stamps are assigned to information blocks stored on said record carrier. In order to provide a secure method for distinguishing between an original and a copy it is proposed according to the present invention that the timing of said time stamps assigned to subsequent information blocks comprises at least one discontinuity and that said at least one discontinuity is used to encode user information.

The invention relates to a method of copy detection of a record carrierwherein time stamps are assigned to information blocks stored on saidrecord carrier. The invention relates further to a method of read-out ofsuch a record carrier, to corresponding apparatuses, to such a recordcarrier itself and to a computer program for implementing said methods.

WO 98/03973 A2 discloses an optical disc and an optical disc recordingapparatus which provide protection against undesired or illegal copying.While address labels assigned to sectors of the optical disc generallyincrease linearly, the address labels of specific sectors, which mayhave an informationless content, are given, e.g. zero, address values inorder to prevent copying CD-ROM discs on a standard CD recorderapparatus.

It is often desired to distinguish between an original and a copiedrecord carrier in an easy way. Therefore, often a unique identifier isassigned to and stored on a record carrier, e.g. by a distributor or asales point of said record carrier. It is therefore an object of thepresent invention to provide a method of copy detection and protectionof a record carrier which allows a replay device to distinguish betweenan original and a copy of a record carrier with high reliability.Further, a corresponding method of read-out of such a record carriershall be provided.

This object is achieved according to the present invention by a methodas claimed in claim 1 according to which the timing of the time stampsassigned to subsequent information blocks comprises at least onediscontinuity and wherein said at least one discontinuity is used toencode user information. Said discontinuity is designed such that areplay device can read said record carrier. However, when copying such arecord carrier, e.g. to a R/RW disc, such discontinuities will becorrected so that the copy will have a continuous timing. Thus, thepresence of discontinuities in the timing of the time stamps can be usedas an indication if the record carrier is an original or a copy.Further, user information is encoded by use of said at least onediscontinuity. For instance, a secure unique identifier can be encoded.If any discontinuities in the timing of the time stamps are corrected ona copy which correction is usually done by a recording device such asecure unique identifier can then not be decoded by a read-out devicewhen accessing such a copy.

Preferred embodiments of the invention are defined in the dependentclaims. A method of read-out of a record carrier is defined in claim 6,comprising the steps of:

reading said time stamps from said record carrier, and

decoding said time stamps to obtain said user information encodedtherein.

A corresponding apparatus for a copy detection and an apparatus forread-out of a record carrier are defined in claims 7 and 8. A recordcarrier according to the present invention is defined in claim 9. Theinvention still further relates to a computer program for implementingthe methods according to the present invention as claimed in claim 10.

The invention will now be explained more in detail with reference to theFigures, in which:

FIG. 1 shows a first possibility of a discontinuity,

FIG. 2 shows a second possibility of a discontinuity,

FIG. 3 shows a third possibility of a discontinuity,

FIG. 4 shows a block diagram of an encoder according to the invention,and

FIG. 5 shows a block diagram of a decoder according to the invention.

FIG. 1 shows a first possibility of providing a discontinuity in thetiming of time stamps assigned to information blocks stored on a recordcarrier such as an optical disc. Usually, the timing is continuous, i.e.time stamps assigned to subsequent information blocks are continuous andincrease linearly. However, according to said embodiment of theinvention, on a fixed location in the lead-in area of the recordcarrier, the subcode timing has a jump in time. In the shown example thesubcode frame 97:49:74 is followed by a subcode frame 98:00:00, i.e.there is a time jump in the subcode timing. While this is a simpleexample, every title can have a different jump length.

Another simple possibility of a discontinuity is shown in FIG. 2 wherein the lead-in area the subcode time is first decreased and thereafter,after a linearly increasing portion, increased by a jump in time back tothe original linearly increasing timing line.

A read-out device accessing a record carrier having such discontinuitiescan, after a firmware change, at least detect such discontinuities oreven measure the length of the time jump. This means that userinformation can be encoded into said discontinuities, e.g. into the way,length and/or positions of time jumps.

A third possibility of providing discontinuities in a certain time-jumparea in the lead-in area of a disc is shown in FIG. 3. Therein, thetiming is modulated in order to encode a bit sequence “0110”. As shown,a sequence of a negative time jump followed by a positive time jump,“negative” meaning a decrease in time and “positive” meaning an increasein time, shall be interpreted as a bit having value zero, while a timejump sequence of a positive time jump followed by a negative time jumpshall be interpreted as bit having value one. In this way a particularuser information can be encoded into discontinuities of the timing.

A block diagram of an encoder according to the present invention isshown in FIG. 4. Therein content is encoded into main channel data by amain channel data unit 1, and additional information such as table ofcontent information and track-timing information is encoded into subcodedata by a subcode data unit 2. Further, an unprotected UDI (Unique DiscIdentifier) uniquely identifying the disc on which said data shall bestored is embedded in said subcode data. It should be noted, that,generally, a UDI can be stored anywhere, i.e. in main channel data orsubcode data.

A hash function unit 3 is provided according to the present invention togenerate a secure UDI if a particular application or replay devicerequires a high certainty that the UDI originates from a read-only disc,but not from a copy. Said hash function unit 3 has as inputs theunprotected UDI and, in the particular example shown in FIG. 4, a numbergenerated from a ROM feature. Such a ROM feature could be the way inwhich the timing is modulated to embed discontinuities in the timing asshown in FIGS. 1 to 3. The output of the hash function unit 3 is asecure UDI. Said ROM feature is also provided to the subcode data unit 2in order to modulate the timing so as to insert such discontinuitieswhich can then be used by a read-out device for generating said secureUDI.

An EFM modulator 4 is further provided for interleaving and modulatingthe main channel data and the subcode data into a channel bit streamwhich is finally recorded on a disc by a laser beam recorder 5.

FIG. 5 shows a block diagram of a decoder according to the presentinvention which is adapted for detection if the accessed disc is anoriginal or a copy. Therein an optical pick-up unit 6 is provided foraccessing and reading a disc. The read channel bit stream is demodulatedby an EFM demodulator 7 into main channel data processed by a mainchannel data unit 8 into the actual content and into subcode dataprocessed by a subcode data unit 9. From said subcode data theunprotected UDI can be retrieved. Said unprotected UDI is also providedto a hash function unit 10 which is similar or identical to the hashfunction unit 3 of the encoder. As second input the described ROMfeature detected from the accessed disc is provided to the hash functionunit 10, i.e. any discontinuities of the timing, in particular of thesubcode data and/or in the lead-in area, which, together with theunprotected UDI, allow the calculation of the secure UDI. If nodiscontinuities can be detected, as will be the case for a copied disc,the secure UDI can not be generated. Thus, an efficient and securemethod of distinguishing between an original and a copy is providedaccording to the present invention.

1. Method of copy detection of a record carrier wherein time stamps areassigned to information blocks stored on said record carrier,characterized in that the timing of said time stamps assigned tosubsequent information blocks comprises at least one discontinuity andthat said at least one discontinuity is used to encode user information.2. Method according to claim 1, wherein said at least one discontinuityis used to encode a unique identifier uniquely identifying said recordcarrier.
 3. Method according to claim 2, wherein said unique identifieris stored in the subcode Q-channel, particularly of an optical recordingsystem for read-only optical discs.
 4. Method according to claim 1,wherein said at least one discontinuity only appears at predeterminedpositions in the lead-in area lead-out area and/or program area of anoptical record carrier.
 5. Method according to claim 1, whereindifferent types of discontinuities are applied for different pieces ofcontent stored on a record carrier.
 6. Method of read-out of a recordcarrier wherein time stamps are assigned to information blocks stored onsaid record carrier such that the timing of said time stamps assigned tosubsequent information blocks comprises at least one discontinuity andthat said at least one discontinuity is used to encode user information,comprising the steps of: reading said time stamps from said recordcarrier, and decoding said time stamps to obtain said user informationencoded therein.
 7. Apparatus for copy detection of a record carrierwherein time stamps are assigned to information blocks stored on saidrecord carrier, characterized by means for assigning said time stamps tosubsequent information blocks such that the timing of said time stampscomprises at least one discontinuity and by means for encoding userinformation into said at least one discontinuity.
 8. Apparatus forread-out of a record carrier wherein time stamps are assigned toinformation blocks stored on said record carrier such that the timing ofsaid time stamps assigned to subsequent information blocks comprises atleast one discontinuity and that said at least one discontinuity is usedto encode user information, comprising: means for reading said timestamps from said record carrier, and means for decoding said time stampsto obtain said user information encoded therein.
 9. Record carrierwherein time stamps or assigned to information blocks stored on saidrecord carrier, characterized in that the timing of said time stampsassigned to subsequent information blocks comprises at least onediscontinuity and that into said at least one discontinuity is userinformation is encoded.
 10. Computer program for implementing the methodof claim 1 comprising program code means for causing a computer toperform the steps of the method as claimed in claim 1 when said computerprogram is run on a computer.